1. Field of the Invention
The invention relates to a hydrodynamic coupling.
2. Description of the Related Art
Hydrodynamic couplings are known for many application cases in many embodiments. An application case of a hydrodynamic coupling in a turbo compound system is disclosed in the reference DE 92 02 578.1. This coupling is connected to the lubricating oil circulation of the internal combustion engine and uses this oil as an operating medium and coolant. From this document it is known that when using motor oil as an operating medium in hydrodynamic couplings, complications can result by impurities in the oil settling on the inside of the circumferential wall of the coupling, which can lead to a block of the coupling and to a loss of its capacity to offset the torque and rotational speed fluctuations. Since the entire coupling rotates, it acts like a centrifugal oil filter. Pump blades and turbine blades of the coupling are manufactured with a high form precision and surface quality, so that between the pump wheel and the turbine wheel, a circulatory flow finds optimal flow-through ratios and thus leads to a high degree of efficiency of the coupling. Because of the design of the blade mounting and the flow circulating between the turbine wheel and pump wheel, the danger of a deposition of solids on the blade mounting itself is generally negligible. Problems are caused by the condition, however, when the motor oil used as an operating medium leaves the operating chamber formed from the blades and thus no longer is found in the circular and rinsing flow between the blades, but instead is only exposed to the centrifugal force generated by the rotation of the coupling. Impurities in the oil are then centrifuged on account of their higher specific gravity, against the circumferential wall of the coupling where a danger of deposition certainly then occurs, when the inside of the circumferential has unevenness in the form of projections, recesses or edges or an insufficient surface quality. In case the primary side of the coupling gets caught on the secondary side due to deposits, then a rigid connection between the primary side and the secondary side results from this, such that during rotary oscillations of the crankshaft of the internal combustion engine, a damage can result either to the coupling or to the drive parts operating together with it. Furthermore, solid deposits in the coupling can also harm the flow in the coupling, which can lead to an increase of the operating temperature and as a result to a damage of the coupling. Another essential problem is the unbalanced mass generated by the deposit, which causes bending vibrations. If the primary side of the coupling touches the secondary side due to deposits, then an additional transmission of torque results from this. In order to avoid this disadvantageous effect, it is proposed in this document that hydrodynamic couplings contain a pump wheel and a turbine wheel, which are connected with a shaft and where the individual blade wheels each form a half-toroidal ring that face each other, have a blade holder and thus form a toroid-shaped operating chamber, and where one of these blade wheels has a housing that is affixed to its radial outer edge, extends radially to the inside and surrounds the rear side of the other wheel, in order to provide the inner side of the housing that faces the rear side of the other wheel with a coating that is friction-reducing and/or inhibitive to solid depositions. This coating generates a very smooth surface, which however, only minimizes the possibility for the depositions, but does not eliminate them. Furthermore, the application of a coating means an increased expense and damages in the coating reduce the success and create additional deposit surfaces.
The purpose of the invention is therefore to further develop a hydrodynamic coupling for use in drive systems which have an operating medium flowing through them in such a way that the problem of the depositions is ruled out to the maximum possible extent. The solution according to the invention should in the process be characterized by as small as possible expense for construction and manufacturing technology.
The solution according to the invention is characterized by the characteristics of claim 1. Advantageous embodiments are described in the subordinate claims.